The proposed research is based on the original observation that after dissociative extractions (3M guanidinium chloride) of nasal cartilage, approximately 10 percent of the proteoglycans remain unextracted in the tissue. When these experiments were carried out with epiphyseal cartilage, it was shown that different amounts of "unextractable" proteoglycans remained in tissue areas in direct correlation to the state of differentiation and/or calcification. Ultrastructural investigations indicate that these unextracted proteoglycans seem to be located in the lacunar area of the chondrocytes. Recent data indicate that hyaluronic acid remains unextractable. A major effect of the proposed work will be directed toward the isolation and purification of hyaluronic acid from cartilage. Histological studies will complement these biochemical investigations.